Rule Engine

Latest stable Based on Bluetape4k release 1.11.0

Problem

A lightweight rule engine library for Kotlin. It follows the Easy Rules pattern and adds Kotlin DSLs, coroutine support (SuspendRule), and annotation-based rule definitions. This manual connects that purpose to the current build, source entry points, tests, configuration resources, and lifecycle evidence instead of duplicating the README feature list.

When to use

Use bluetape4k-rule-engine when the application needs input contracts, value semantics, algorithmic cost, and deterministic output. Start with the source entry points below and confirm that their ownership and failure contracts match the calling component. Prefer a smaller standard-library or already-adopted module when it satisfies the same contract without another runtime boundary.

Coordinates

dependencies {
    implementation(platform("io.github.bluetape4k:bluetape4k-dependencies:<version>"))
    implementation("io.github.bluetape4k:bluetape4k-rule-engine")
}

Gradle project path: :bluetape4k-rule-engine. Source directory: utils/rule-engine.

Concepts

The first source-level concepts to inspect are RuleDefaults, Action, Condition, Fact, Priority, Rule, Action, and Condition. File names are navigation anchors; read each declaration and its tests before treating it as a public contract.

Quick start

Add the coordinate above, refresh Gradle, and start from the smallest entry point that owns the required task. Open RuleDefaults first; it is a concrete source entry point for the module.

API by task

Entry point	What to verify
`RuleDefaults`	Inspect this declaration’s constructors, functions, and ownership contract.
`Action`	Inspect this declaration’s constructors, functions, and ownership contract.
`Condition`	Inspect this declaration’s constructors, functions, and ownership contract.
`Fact`	Inspect this declaration’s constructors, functions, and ownership contract.
`Priority`	Inspect this declaration’s constructors, functions, and ownership contract.
`Rule`	Inspect this declaration’s constructors, functions, and ownership contract.
`Action`	Inspect this declaration’s constructors, functions, and ownership contract.
`Condition`	Inspect this declaration’s constructors, functions, and ownership contract.
`Facts`	Inspect this declaration’s constructors, functions, and ownership contract.
`Rule`	Inspect this declaration’s constructors, functions, and ownership contract.

Patterns

The README evidence is organized around Architecture, Concept Overview, Core Class Diagram, Rule Engine Class Diagram, Composite Rules, Rule Execution Sequence, InferenceRuleEngine (Forward Chaining), Rule Engine Selection Guide, Core Features, and Usage Examples. Use those topics as a navigation map, then confirm behavior in source and tests. Keep adoption narrow and connect owned resources to the caller lifecycle.

Integrations

The current build declares these integration edges:

api(project(":bluetape4k-core"))
implementation(project(":bluetape4k-coroutines"))
implementation(libs.kotlinx.coroutines.core)
implementation(platform(libs.spring.boot.dependencies))
compileOnly("org.springframework:spring-expression")
compileOnly(libs.mvel2)
compileOnly(libs.janino)
compileOnly(libs.janino.commons.compiler)
compileOnly(libs.groovy)
compileOnly(libs.kotlin.scripting.common)
compileOnly(libs.kotlin.scripting.jvm)
compileOnly(libs.kotlin.scripting.jvm.host)

Treat compileOnly edges as caller-provided capabilities and verify runtime availability before using their APIs.

Configuration

No module-level configuration resource was found under src/main/resources. Configuration is supplied through constructors, builders, function arguments, or the integrating framework; confirm defaults in source.

Failures

Failure semantics are defined by the linked entry points and tests, not inferred from the artifact name. Keep cancellation and timeout signals intact, close owned resources, and translate backend exceptions only at a boundary that can add a stable domain contract. Use the test anchors below to verify the exact behavior before adding retries or fallbacks.

Operations

Measure hot paths, bound input sizes, and monitor failures at the application boundary that calls the utility. Keep capacity, timeout, retry, and shutdown settings next to the component that owns the resource; avoid process-wide defaults that hide which caller accepted the trade-off.

Testing

Run the module test task:

./gradlew :bluetape4k-rule-engine:test --no-configuration-cache

Representative test anchors:

Workshops

No dedicated workshop path is registered in the manual manifest. Use the module README and the representative tests above as runnable evidence.

Limitations

This page documents the repository state represented by the linked source and tests. It does not turn optional backends into application defaults or claim performance without a benchmark artifact. Re-check compatibility and lifecycle notes when the module version changes.

Release diagrams

These diagrams are loaded directly from README assets published with the 1.11.0 release and pinned to its immutable commit. They describe this manual’s released structure and runtime flows, not later Snapshot changes. Select a preview to open the SVG at the same release commit.

Rule Engine

Problem

When to use

Coordinates

Concepts

Quick start

API by task

Patterns

Integrations

Configuration

Failures

Operations

Testing

Workshops

Limitations

Release diagrams

Rule Engine Concept Overview diagram

Core Class Diagram diagram

Rule Engine Class Diagram

Composite Rules diagram

InferenceRuleEngine (Forward Chaining) diagram

Rule Engine Selection Guide diagram

Script Engine Selection Guide diagram

Rule Execution Sequence diagram

Sources